Copending application U.S. Ser. No. 08/123,839 of Douglas A. Smith, John F. Carson, Roy B. Ference and Karen J. Appel, entitled METHOD AND APPARATUS FOR EXPOSING PHOTOSENSITIVE MEDIA WITH MULTIPLE LIGHT SOURCES, filed Sep. 20, 1993, discloses a method and apparatus for exposing photosensitive media with multiple light sources, and which is hereby incorporated by reference. In this patent application, an LED print head is disposed on the outer surface of a spinning rotor which exposes light onto a photosensitive material, such as photographic paper. In such a mechanism there are very stringent performance requirements on the positioning and/or velocity accuracy of the translator mechanism. High accuracy of motion is required to prevent well-known banding artifacts which can be easily perceived by human vision. These artifacts typically can be caused by a variety of positional error sources within the digital printing apparatus. In linear translator-type mechanisms, there are two major components which control the overall accuracy of motion. The first is the driver assembly, which in the case of the copending application is a high-helix, rolled-threaded lead screw driven by a rotary stepper motor. The second major component is the guidance assembly by which the carriage travels linearly along a predetermined path. Typically, the carriage is attached to a pair of parallel shafts by roller elements which allow the carriage to travel along the linear path.
The present invention provides a very accurate and smooth carriage motion for linear translation of the carriage which is relatively low in cost to construct and assemble and minimizes the artifact problems which can arise from such devices.